diff --git a/lib/script/interpreter.js b/lib/script/interpreter.js
index 4c0d79954..97116486d 100644
--- a/lib/script/interpreter.js
+++ b/lib/script/interpreter.js
@@ -9,6 +9,7 @@ var Hash = require('../crypto/hash');
 var Signature = require('../crypto/signature');
 var PublicKey = require('../publickey');
 
+
 /**
  * Bitcoin transactions contain scripts. Each input has a script called the
  * scriptSig, and each output has a script called the scriptPubkey. To validate
@@ -402,6 +403,92 @@ Interpreter.prototype.checkPubkeyEncoding = function(buf) {
   return true;
 };
 
+
+
+/**
+  *
+  * Check the buffer is minimally encoded (see https://github.com/bitcoincashorg/spec/blob/master/may-2018-reenabled-opcodes.md#op_bin2num)
+  *
+  *
+  */
+
+Interpreter._isMinimallyEncoded = function(buf) {
+  if (buf.length >  Interpreter.MAX_SCRIPT_ELEMENT_SIZE ) {
+      return false;
+  }
+
+  if (buf.length > 0) {
+      // Check that the number is encoded with the minimum possible number
+      // of bytes.
+      //
+      // If the most-significant-byte - excluding the sign bit - is zero
+      // then we're not minimal. Note how this test also rejects the
+      // negative-zero encoding, 0x80.
+      if ((buf[buf.length-1] & 0x7f) == 0) {
+          // One exception: if there's more than one byte and the most
+          // significant bit of the second-most-significant-byte is set it
+          // would conflict with the sign bit. An example of this case is
+          // +-255, which encode to 0xff00 and 0xff80 respectively.
+          // (big-endian).
+          if (buf.length <= 1 || (buf[buf.length - 2] & 0x80) == 0) {
+              return false;
+          }
+      }
+  }
+  return true;
+};
+
+/**
+  *
+  * minimally encode the buffer content
+  *
+  * @param {number} nMaxNumSize (max allowed size)
+  */
+Interpreter._minimallyEncode = function(buf) {
+    if (buf.length == 0) {
+        return buf;
+    }
+
+    // If the last byte is not 0x00 or 0x80, we are minimally encoded.
+    var last = buf[buf.length - 1];
+    if (last & 0x7f) {
+        return buf;
+    }
+
+    // If the script is one byte long, then we have a zero, which encodes as an
+    // empty array.
+    if (buf.length == 1) {
+      return Buffer.from('');
+    }
+
+    // If the next byte has it sign bit set, then we are minimaly encoded.
+    if (buf[buf.length - 2] & 0x80) {
+        return buf;
+    }
+
+    // We are not minimally encoded, we need to figure out how much to trim.
+    for (var i = buf.length - 1; i > 0; i--) {
+        // We found a non zero byte, time to encode.
+        if (buf[i - 1] != 0) {
+            if (buf[i - 1] & 0x80) {
+                // We found a byte with it sign bit set so we need one more
+                // byte.
+                buf[i++] = last;
+            } else {
+                // the sign bit is clear, we can use it.
+                buf[i - 1] |= last;
+            }
+
+            return buf.slice(0,i);
+        }
+    }
+
+    // If we the whole thing is zeros, then we have a zero.
+    return Buffer.from('');
+}
+
+
+
 /**
  * Based on bitcoind's EvalScript function, with the inner loop moved to
  * Interpreter.prototype.step()
@@ -427,6 +514,7 @@ Interpreter.prototype.evaluate = function() {
       return false;
     }
   } catch (e) {
+
     this.errstr = 'SCRIPT_ERR_UNKNOWN_ERROR: ' + e;
     return false;
   }
@@ -567,8 +655,6 @@ Interpreter.prototype.step = function() {
       case Opcode.OP_CAT:
       case Opcode.OP_SPLIT:
 
-      case Opcode.OP_NUM2BIN:
-      case Opcode.OP_BIN2NUM:
       case Opcode.OP_DIV:
       case Opcode.OP_MOD:
 
@@ -578,6 +664,8 @@ Interpreter.prototype.step = function() {
       case Opcode.OP_AND:
       case Opcode.OP_OR:
       case Opcode.OP_XOR:
+      case Opcode.OP_BIN2NUM:
+      case Opcode.OP_NUM2BIN:
         // Opcodes that have been reenabled.
         if ((self.flags & Interpreter.SCRIPT_ENABLE_MONOLITH_OPCODES) == 0) {
           return true;
@@ -1592,6 +1680,88 @@ Interpreter.prototype.step = function() {
         }
         break;
 
+        //
+        // Conversion operations
+        //
+        case Opcode.OP_NUM2BIN: {
+
+          // (in -- out)
+          if (this.stack.length < 2) {
+            this.errstr = 'SCRIPT_ERR_INVALID_STACK_OPERATION';
+            return false;
+          }
+
+          var size = BN.fromScriptNumBuffer(stacktop(-1), fRequireMinimal).toNumber();
+          if (size > Interpreter.MAX_SCRIPT_ELEMENT_SIZE) {
+            this.errstr = 'SCRIPT_ERR_PUSH_SIZE';
+            return false;
+          }
+
+          this.stack.pop();
+          var rawnum = stacktop(-1);
+
+          // Try to see if we can fit that number in the number of
+          // byte requested.
+          rawnum=Interpreter._minimallyEncode(rawnum);
+
+          if (rawnum.length > size) {
+            // We definitively cannot.
+            this.errstr = 'SCRIPT_ERR_IMPOSSIBLE_ENCODING';
+            return false;
+          }
+
+          // We already have an element of the right size, we
+          // don't need to do anything.
+          if (rawnum.length == size) {
+            this.stack[this.stack.length-1] = rawnum;
+            break;
+          }
+
+          var signbit = 0x00;
+          if (rawnum.length > 0) {
+            signbit = rawnum[rawnum.length - 1] & 0x80;
+            rawnum[rawnum.length - 1] &= 0x7f;
+          }
+
+          var num = Buffer.alloc(size);
+          rawnum.copy(num,0);
+
+          var l = rawnum.length - 1;
+          while (l++ < size - 2) {
+            num[l]=0x00;
+          }
+
+          num[l]=signbit;
+
+          this.stack[this.stack.length-1] = num;
+        } 
+        break;
+
+
+
+        case Opcode.OP_BIN2NUM: {
+          // (in -- out)
+          if (this.stack.length < 1) {
+            this.errstr = 'SCRIPT_ERR_INVALID_STACK_OPERATION';
+            return false;
+          }
+
+          buf1 = stacktop(-1);
+          buf2 = Interpreter._minimallyEncode(buf1);
+
+          this.stack[this.stack.length - 1] = buf2;
+
+          // The resulting number must be a valid number.
+          if (!Interpreter._isMinimallyEncoded(buf2)) {
+            this.errstr = 'SCRIPT_ERR_INVALID_NUMBER_RANGE';
+            return false;
+          }
+        } 
+        break;        
+
+
+
+
       default:
         this.errstr = 'SCRIPT_ERR_BAD_OPCODE';
         return false;
diff --git a/lib/script/script.js b/lib/script/script.js
index ad6b62a7d..966039ec5 100644
--- a/lib/script/script.js
+++ b/lib/script/script.js
@@ -689,6 +689,7 @@ Script.prototype._addBuffer = function(buf, prepend) {
   return this;
 };
 
+
 Script.prototype.removeCodeseparators = function() {
   var chunks = [];
   for (var i = 0; i < this.chunks.length; i++) {
diff --git a/lib/util/buffer.js b/lib/util/buffer.js
index 3c126199c..852801bb1 100644
--- a/lib/util/buffer.js
+++ b/lib/util/buffer.js
@@ -170,7 +170,7 @@ module.exports = {
   hexToBuffer: function hexToBuffer(string) {
     assert(js.isHexa(string));
     return new buffer.Buffer(string, 'hex');
-  }
+  },
 };
 
 module.exports.NULL_HASH = module.exports.fill(Buffer.alloc(32), 0);
diff --git a/test/script/interpreter.js b/test/script/interpreter.js
index 9b056ca53..4f34af98f 100644
--- a/test/script/interpreter.js
+++ b/test/script/interpreter.js
@@ -285,7 +285,7 @@ describe('Interpreter', function() {
 
         // Temporary, until all reenable opcodes are implemented  
         // 
-        var pendingToImplement = ['NUM2BIN', 'BIN2NUM', 'CAT','SPLIT', 'DIV', 'MOD'];
+        var pendingToImplement = ['CAT','SPLIT', 'DIV', 'MOD'];
         function isPendingToImplement(str) {
           for(var i in pendingToImplement) {
             if (fullScriptString.indexOf(pendingToImplement[i])!=-1) {